import java.util.Scanner;
public class BYZ {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int a = 26;
        int b = a * a;
        int dp = 2021 - a - b;
        int c = 0;
        for (int i = 1; i <=26 ; i++) {
            for (int j = 1; j <=26; j++) {
                for (int k = 1; k <=26; k++) {
                    c++;
                    if(c==dp){
                        System.out.println((char)(i+64)+""+(char)(j+64)+""+(char)(k+64));
                        break;
                    }
                }
            }
        }
    }
}
